This application relates to magnetic disc drives and more particularly to an apparatus for latching a disc drive actuator mechanism in a parked position when the drive is de-energized.
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces. The actuator thus allows the head to move back and forth in an arcuate fashion between an inner radius and an outer radius of the discs.
When the drive is de-energized or shut down, the drive motor stops spinning and the actuator is rotated, for example, counterclockwise to position the heads at an inner diameter landing zone location and latch the actuator in this position. Often a magnetic latch is used to maintain the actuator in this position with the heads in the landing zone. When a magnetic latch is used, an inadvertent external shock load, such as the drive being dropped, may cause sufficient rotational force to be applied to the actuator arms to overcome the magnetic attraction and thus the actuator arm may rotate from the landing zone to the data region of the discs without the discs spinning at all. This could destroy the stored data and could destroy the heads themselves. Consequently there is a need for a latch mechanism that ensures that the actuator stays in the parked position any time that the disc drive motor is deenergized and, more importantly, the discs are not spinning.
This deenergized latching has been traditionally accomplished by a wind operated latching mechanism which utilizes wind generated by the spinning discs while the drive motor is energized to push against a pivoting air filter member positioned adjacent the outer margin of the discs. This air filter member has a pivot portion, an air filter portion, and an elongated air vane which extends outward over the top disc in the disc stack. Air drawn along the surface of the disc toward the outer disc rim constitutes a wind that generates a force which pushes against the air vane producing a moment arm in a clockwise direction on the pivoting air filter member. At the other end of the pivot portion of the air filter member is an elongated latch arm and a tab portion that carries a steel ball therein. The steel ball in the tab portion is positioned in the magnetic field generated by the VCM magnets and thus biases the latch counterclockwise such that the latch arm interferes with movement of the actuator arm off of the magnetic latch when the drive is deenergized.
The operation of this conventional latch mechanism is completely automatic, driven only by the VCM magnet magnetic field bias and the force exerted by wind against the air filter and air vane when the discs are spinning at normal speed. The size and placement of the steel ball on the tab portion are dictated by the requirement that the latch be disengaged when the discs are operating at full speed and engaged when the discs are turning at less than full operating speed with the actuator arm moved into the parked position.
The conventional air vane design has worked well for drives with three or four or more operating discs in the head disc assembly (HDA). However, in the case of drives designed for four discs and having only one or two discs installed in the HDA, there have been cases where the air vane latches failed to rotate and move to the disengaged position when the drive is energized, thus preventing actuator movement and appearing to the user by the software as a disc crash or disc drive failure. In these cases, the failures appear to have occurred at high altitudes and/or elevated temperatures, i.e. under conditions of reduced atmospheric pressure. Accordingly, there is a need for a wind operated latching apparatus for use in disc drives having only one or two discs which automatically disengages the actuator arm when the disc drive motor spins the discs at operating speed and engages the actuator arm when the disc or discs spin at less than operating speed and the actuator arm is in the parked position in a head disc assembly (HDA) designed to accommodate up to four or more discs.
Against this backdrop the present invention has been developed. The present invention is an air filter having a dual air vane arrangement with one air vane adapted to extend over the upper surface of a top disc on the disc drive motor and another, supplemental air vane beneath the top disc adapted to extend under the underside surface of the top disc. This arrangement provides an additional moment arm on the pivoting air filter when only one or two discs are located on the drive motor in the HDA. This supplemental air vane is positioned adjacent the outer perimeter of the disc or discs and extends from the air filter portion of the latch member thus capturing additional air flow and thus providing an additional moment arm on the air filter latch when the drive is utilized at high elevations where the air is thinner or at elevated temperatures at which the air is less dense. This additional air vane permits a larger steel ball to be utilized in the latch apparatus thereby ensuring more positive latch and unlatch operations of the apparatus.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.